Method and system for dual mode operation in wireless networks

ABSTRACT

Aspects of a method and system for dual mode operation in wireless networks are presented. Aspects of the system include a communicating device that selects an RF channel and a physical layer type. The communicating device may process signals received via the selected RF channel based on the selected physical layer type. The communicating device may determine whether a beacon frame has been detected base on the signals that were received via the selected RF channel and processed based on the selected physical layer type. When a frame is not detected, the communicating device may determine a signal energy level for the received signals. The communicating device may establish an association with an existing network based on detection of the beacon frame or the communicating device may transmit an originating beacon frame based on the determined signal energy level.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application makes reference to, claims priority to, and claims thebenefit of:

-   U.S. Provisional Application Ser. No. 61/035,694 filed Mar. 11,    2008, and-   U.S. Provisional Application Ser. No. 61/051,526 filed on May 8,    2008.

Each of the above stated applications is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to wireless communication.More specifically, certain embodiments of the invention relate to amethod and system for dual mode operation in wireless networks.

BACKGROUND OF THE INVENTION

IEEE 802.15 describes a communication architecture, which may enablecommunicating devices (DEVs) to communicate via wireless personal areanetworks (WPANs). Many DEVs utilized in WPANs are small or handhelddevices, such as personal digital assistants, portable computers, orconsumer electronics devices such as digital video recorders or set topboxes. IEEE 802.15 is a short-range wireless communications standardthat enables connection between consumer and computer equipment whileeliminating wires. IEEE 802.15 WPAN DEVs may utilize frequencies in the57 GHz to 66 GHz range for communication.

A plurality of communicating DEVs in a WPAN environment may comprise anetwork known as a piconet. One of the DEVs in a piconet may function asa piconet coordinator (or controller), or PNC. The PNC may provideoverall coordination for the communication between DEVs in a piconet.The piconet may comprise the PNC and DEVs, which are associated with thePNC.

Communications between communicating DEVs in a WPAN may occur withintime intervals referred to as superframes. The superframe may comprise aplurality of segments. In a first superframe segment, the PNC maytransmit one or more beacon frames. The beacon frame may enablerecipient DEVs to identify the PNC. The beacon frame may also enablerecipient DEVs to identify other DEVs, which are currently associatedwith PNC within the piconet. In addition, a beacon frame may indicatetime durations within the current superframe during which assigned DEVsmay transmit and/or receive signals via a wireless communication medium.These time durations may be referred to as time slots. The time slotassignments may be in response to requests received from the DEVs duringone or more previous superframes.

A second superframe segment may comprise a contention access period(CAP). The starting time instant and time duration of the CAP may becommunicated within the preceding beacon frame. During the CAP, the DEVsmay respond to the beacon frames by communicating with the PNC toestablish an association within the piconet. Associations establishedduring a current superframe may be reported via beacon frames in one ormore subsequent superframes.

The DEVs within the piconet may also utilize the CAP to communicate datato other DEVs. Communicating DEVs may attempt to gain access to thewireless communication medium before attempting to transmit data. Thecollision sense multiple access with collision avoidance (CSMA/CA)protocol is typically utilized by communicating devices for wirelessmedium access. During the CAP, a DEV seeking medium access, anoriginating DEV, may transmit a request to send (RTS) frame. The RTSframe may be addressed to a destination DEV but the RTS frame may bereceived by other DEVs. The destination DEV may respond to the RTS frameby transmitting a clear to send (CTS) frame. The originating DEV anddestination DEV may subsequently commence communication via the wirelessmedium. The communications may, for example, involve the transmission ofdata frames between the originating DEV and the destination DEV. Directcommunications between an originating DEV and a destination DEV duringthe CAP are typically intermittent communications, which compriserelatively short time durations. In accordance with the CSMA/CAprotocol, other DEVs that receive the RTS frame transmitted by theoriginating DEV may refrain from transmitting signals via the wirelessmedium during these communications. When an originating DEV seeks toreserve access to the wireless medium for longer time durations, theoriginating DEV may transmit an RTS frame to the PNC during the CAP. ThePNC may respond to the originating RTS frame by sending anacknowledgment frame that comprises a time allocation slot.

A third superframe segment may comprise a channel time allocation (CTA)period. The CTA period may comprise one or more CTA time slots. Duringthe CTA period, the PNC may assign and/or schedule a set of CTA timeslots to one or more DEVs within the piconet. The PNC may communicate atime allocation slot to an assigned DEV during the CAP that identifies aspecific CTA time slot. During the assigned CTA time slot the assignedDEV may be granted reserved access to the wireless communication medium.The assigned DEV may utilize the assigned CTA time slot to engage incommunications with one or more destination DEVs. Other DEVs, which arenot engaged in communications with the originating DEV, may refrain fromtransmitting signals via the wireless communication medium during theassigned CTA time slot. In conventional piconet systems, an individualCTA time slot is assigned to a single DEV. Thus, a single DEV maytransmit signals via the wireless communication medium during a givenCTA time slot.

The CTA period may also comprise a management CTA (MCTA) period. Duringthe MCTA period, the DEVs may request CTA time slot assignments from thePNC. The PNC may respond to CTA time slot allocation requests receivedin the current superframe by making CTA time slot assignments for one ormore subsequent superframes. The time slot assignments may be reportedvia beacon frames transmitted during the respective subsequentsuperframes.

The 57 GHz to 66 GHz frequency band may be utilized by different typesof DEVs. The different types of DEVs may be utilized in connection witha variety of applications, which have different requirements.

The DEVs utilized in connection with digital video applications, forexample video display, digital video recorder (DVR) and/or set top box(STB) devices may operate at data throughput rates that are in excess of3 Gbps. Wireless communications between the video display, DVR and/orSTB DEVs may involve transmission and reception of signals that traversenon line of sight (NLOS) signal propagation paths.

Portable computer and docking station DEVs may also operate at datathroughput rates that are in excess of 3 Gbps. Wireless communicationsbetween portable computers and docking station DEVs may occur over lineof sight (LOS) and/or NLOS signal propagation paths.

Hand-held DEVs may operate at data throughput rates that are in excessof 1 Gbps. The Hand-held DEVs may communicate wirelessly in connectionwith file sharing, sharing of digital audio content, digital videocontent and/or digital multimedia content, for example. Wirelesscommunications between the hand-held devices typically occur over LOSsignal propagation paths.

Wireless communications between hand-held and portable computer and/ornetwork attached storage (NAS) DEVs may occur within the context of datasynchronization applications. For example, a hand-held DEV may transmitdata stored within the hand-held DEV to a personal computer DEV toenable data synchronization between the data stored in the hand-held DEVand the corresponding data stored in the personal computer DEV. The datastored in a personal computer or NAS DEV may then be accessed via anetwork. Wireless communications between hand-held DEVs and portablecomputer and/or NAS DEVs may involve data throughput rates that are inexcess of 1 Gbps and typically occur over NLOS signal propagation paths.

Within a given DEV, applications may operate within the broaderconstruct of a protocol reference model (PRM). The PRM may comprise aseries of layers that enable communication between DEVs. For example,the PRM may comprise an application layer. The application layer withinthe PRM may correspond to a data source. Other layers within the PRM maycooperate with the application layer to partition the data from the datasource into protocol data units (PDUs), for example, packets or frames,which comprise blocks of bits generated by the data source. At thephysical (PHY) layer, signals may be generated that enable the data tobe transmitted across a wired and/or wireless communication medium. Thecomplexity of the operations performed by the PHY layer may bedetermined based on the application and corresponding requirements.Thus, different DEV types, which are utilized in connection withdifferent applications, may comprise different levels of PHY complexity.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A method and system for dual mode operation in wireless networks,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exemplary wireless communication system, in accordance withan embodiment of the invention.

FIG. 2 is an exemplary hierarchical piconet structure, in accordancewith an embodiment of the invention.

FIG. 3 is a diagram of an exemplary hierarchical superframe, inaccordance with an embodiment of the invention.

FIG. 4 is a diagram of an exemplary communicating device, which may beutilized in connection with an embodiment of the invention.

FIG. 5 is a flowchart that illustrates exemplary steps for beacon framegeneration in a piconet controller, in accordance with an embodiment ofthe invention.

FIG. 6 is a flowchart that illustrates exemplary steps for cold start ofa communicating device, in accordance with an embodiment of theinvention.

FIG. 7 is a diagram of an exemplary protocol data unit, which may beutilized in connection with an embodiment of the invention.

FIG. 8 is a block diagram of an exemplary transmitter, in accordancewith an embodiment of the invention.

FIG. 9 is a block diagram of an exemplary single mode transmitter, inaccordance with an embodiment of the invention.

FIG. 10 is a block diagram of an exemplary dual mode transmitter, inaccordance with an embodiment of the invention.

FIG. 11 is a block diagram of an exemplary dual mode receiver, inaccordance with an embodiment of the invention.

FIG. 12 is a block diagram illustrating exemplary preambles for MIMOoperation, in accordance with an embodiment of the invention.

FIG. 13 is a block diagram of an exemplary IFFT algorithm for low rateOFDM encoding, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor dual mode operation in wireless networks. Various embodiments of theinvention comprise a method and system, which establishes a hierarchicalrelationship among a plurality of piconets. At the base of the hierarchyis a parent piconet. From the parent piconet a plurality of dependentpiconets may be defined. The parent piconet and each of the dependentpiconets may comprise a distinct plurality of DEVs, which communicatewithin the respective piconet within the hierarchy. A piconet controller(PNC) may coordinate communications within the parent piconet and withineach of the respective dependent piconets. The hierarchical piconetstructure may enable sharing of RF channels between the DEVs within aparent piconet and DEVs within a dependent piconet while reducing thelikelihood that the sharing of RF channels will impair the ability ofDEVs within the parent piconet to communicate concurrently withcommunications between DEVs within the dependent piconet.

In various embodiments of the invention, the piconet hierarchy mayenable segregation of DEVs based on PHY complexity. In an exemplaryembodiment of the invention, communicating DEVs within a parent piconetmay utilize orthogonal frequency division multiplexing (OFDM), whilecommunicating DEVs within a dependent piconet may utilize single carriermodulation (SCM). In various embodiments of the invention thesegregation of the DEVs within the hierarchical piconet structure mayenable sharing of RF channels between the DEVs within a parent piconetand DEVs within a dependent piconet. This may enable communicating DEVsin the parent piconet and in the dependent piconet to concurrentlyutilize the one or more common RF channels, while reducing thelikelihood that the concurrent sharing of RF channels will impaircommunications between the DEVs within the parent piconet, which utilizean OFDM PHY, when there are also communications between the DEVs withinthe dependent piconet, which utilize an SCM PHY, for example, and viceversa.

FIG. 1 is an exemplary wireless communication system, in accordance withan embodiment of the invention. Referring to FIG. 1, there is shown anexemplary piconet 100, which comprises a PNC 102 and a plurality of DEVs112, 114, 116 and 118.

The PNC 102 may comprise suitable logic, circuitry, interfaces and/orcode that may be operable to comprise DEV functionality. The PNC 102 maycommunicate beacon frames to each of the DEVs 112, 114, 116 and 118. ThePNC 102 and any of the DEVs, for example, DEV 118, may communicate toexchange data.

Each of the plurality of DEVs 112, 114, 116 and 118 may comprise logic,circuitry, interfaces and/or code that may be operable to communicatewith another DEV to exchange data, for example the DEV 112 and DEV 114,DEV 112 and DEV 116, the DEV 112 and DEV 118 and/or the DEV 116 and DEV118, for example. Communications for data exchange between communicatingDEVs within the piconet 100 may occur during the contention accessperiod (CAP) within a superframe and/or during a channel time allocation(CTA) time slot, for example.

In an exemplary embodiment of the invention, the DEV 114 and the DEV 116may utilize an SCM PHY, while the PNC 102, DEV 112 and DEV 118 mayutilize an SCM PHY and/or an OFDM PHY. In this regard, the DEV 114 andDEV 116 may be referred to as single mode DEVs while the PNC 102, DEV112 and DEV 118 may be referred to as dual mode DEVs. The PNC 102 mayutilize the SCM PHY when transmitting beacon frames. The PNC 102, DEV112 and DEV 118 may utilize the SCM PHY when communicating with otherDEVs within the piconet 100 during the CAP. The PNC 102, DEV 112 and DEV118 may utilize the OFDM PHY when communicating with other DEVs withinthe piconet 100 during the CTA period. The DEV 114 and DEV 116 mayutilize the SCM PHY when communicating with other DEVs within thepiconet 100 during the CAP and during the CTA period.

A DEV that utilizes a given PHY may communicate with other DEVs withinthe piconet 100 that utilize the same PHY. For example, when the DEV 112utilizes an SCM PHY, the DEV 112 may communicate: with the PNC 102 whenthe PNC 102 utilizes an SCM PHY; with the DEV 118 when DEV 118 utilizesan SCM PHY; with the DEV 114; and with the DEV 116. When the DEV 112utilizes an OFDM PHY, the DEV 112 may communicate: with the PNC 102 whenthe PNC 102 utilizes an OFDM PHY; and with the DEV 118 when the DEV 118utilizes an OFDM PHY.

In an exemplary embodiment of the invention, the PNC 102, DEV 112 andDEV 118 may each utilize an SCM PHY during the beacon frame portion of asuperframe and during the CAP portion of the superframe. By doing so,the PNC 102 may communicate with each of the DEVs 112, 114, 116 and 118during the beacon frame and CAP portions of the superframe; the DEV 112may receive beacon frames transmitted by the PNC 102 and may communicatewith the PNC 102 and any of the DEVs 114, 116 and 118 during the CAPportion of the superframe; the DEV 118 may receive beacon framestransmitted by the PNC 102 and may communicate with the PNC 102 and anyof the DEVs 112, 114 and 116 during the CAP portion of the superframe;DEV 114 may receive beacon frames transmitted by the PNC 102 and maycommunicate with the PNC 102 and any of the DEVs 112, 116 and 118 duringthe CAP portion of the superframe; and the DEV 116 may receive beaconframes transmitted by the PNC 102 and may communicate with the PNC 102and any of the DEVs 112, 114 and 118 during the CAP portion of thesuperframe. However, during the CTA period, the DEV 112, the DEV 118 andthe PNC 102 may utilize OFDM PHYs while DEV 114 and DEV 116 utilize SCMPHYs. This may enable, for example, the DEV 112 and DEV 118 to utilize agiven RF channel, while concurrently DEV 114 and DEV 116 utilize thesame RF channel. Because the DEV 112 and DEV 118 utilize a different PHYfrom that utilized by the DEV 114 and DEV 116, the likelihood is reducedthat communications between the DEV 112 and DEV 118 may interfere withconcurrent communications between the DEV 114 and DEV 116, and viceversa.

FIG. 2 is an exemplary hierarchical piconet structure, in accordancewith an embodiment of the invention. Referring to FIG. 2, there is shownan exemplary hierarchical piconet 200. The hierarchical piconet 200comprises a parent piconet 222 and a dependent piconet 224. The parentpiconet 222 comprises a PNC 202 and a plurality of DEVs 212 and 218. ThePNC 202 also comprises DEV functionality. The dependent piconet 224comprises a plurality of DEVs 214 and 216. Communicating DEVs within theparent piconet 222 may utilize an RF channel k, which will be referredto as RF(k). Communicating DEVs within the dependent piconet 224 mayalso utilize the RF channel, RF(k).

In an exemplary embodiment of the invention, the PNC 202 may utilize anSCM PHY and/or an OFDM PHY; the DEVs 212 and 218 may utilize OFDM PHYsand the DEVs 114 and 116 may utilize SCM PHYs. The PNC 202 may utilize aparent superframe in which one or more CTA time slots comprise adependant superframe. For example, when the PNC 202 transmits a beaconframe for the parent superframe, or parent beacon frame, the parentbeacon frame may identify the CTA time slot(s) that is assigned to thedependent superframe. In various embodiments of the invention, the PNC202 may preassign the CTA time slot(s), which are to be utilized for thedependent superframe. The parent beacon frame may also indicate the timeinstant at which the succeeding parent superframe will begin. The PNC202 may utilize an OFDM PHY when transmitting the parent beacon frame.The DEV 212 and DEV 218 may be able to receive the parent beacon framebut the DEV 214 and DEV 216 may be unable to receive the parent beaconframe. Communications for data exchange may occur between the DEV 212and DEV 218 during the CAP portion of the parent superframe and/orduring assigned CTA time slots. Communications for data exchange mayoccur between the PNC 202 and DEV 212 and/or the DEV 218 during the CAPportion of the parent superframe and/or during CTA time slots within theparent superframe when the PNC 202 utilizes an OFDM PHY.

During the CTA time slot assigned to the dependent superframe the PNC202 may transmit a beacon frame for the dependent superframe, ordependent beacon frame. The dependent beacon frame may communicateinformation that is relevant to the dependent superframe, for example,CTA time slot assignments within the dependent superframe. The dependentbeacon frame may also indicate the time instant at which the succeedingdependent superframe will begin. The PNC 202 may utilize an SCM PHY whentransmitting the dependent beacon frame. The DEV 214 and DEV 216 may beable to receive the dependent beacon frame but the DEV 212 and DEV 218may be unable to receive the dependent beacon frame. Communications fordata exchange may occur between the DEV 214 and DEV 216 during the CAPportion of the dependent superframe and/or during assigned CTA timeslots. Communications for data exchange may occur between the PNC 202and DEV 214 and/or DEV 216 during the CAP portion of the dependentsuperframe and/or during CTA time slots within the dependent superframewhen the PNC 202 utilizes an SCM PHY.

FIG. 3 is a diagram of an exemplary hierarchical superframe, inaccordance with an embodiment of the invention. Referring to FIG. 3,there is shown a parent superframe 300. The parent superframe 300 maycomprise a parent beacon 302, a parent CAP 304, a parent managementchannel time allocation time slot (MCTA_1) 306 a, a parent MCTA_2 306 b,and a parent channel time allocation (CTA) period 308. The parent CTAperiod 308 may comprise a plurality of n CTA time slots, CTA_1 312 a,CTA_2 312 b, . . . , CTA_n−1 312 c and CTA_n 312 d. A dependentsuperframe 350 may be assigned to CTA_1 312 a. The dependent superframe350 may comprise a dependent beacon frame 352, a dependent CAP 354, adependent MCTA_1 356 a, a dependent MCTA_2 356 b and a dependent CTAperiod 358. The dependent CTA period 358 may comprise a plurality of mCTA time slots, CTA_1 362 a, CTA_2 362 b, . . . , CTA_m−1 362 c andCTA_m 362 d. During the parent CAP 304, DEVs may join the parent piconet222. During the dependent CAP 354, the DEVs may join the dependentpiconet 224.

In an exemplary embodiment of the invention, the PNC 202 may transmitthe parent beacon frame 302, via an RF channel RF(k), utilizing a PHY,which is utilized for transmitting signals within a parent piconet 222,for example an OFDM PHY. The PNC 202 may transmit the dependent beaconframe 352, via RF(k) utilizing a PHY, which is utilized for transmittingsignals within a dependent piconet 224, for example an SCM PHY. The DEVswithin the parent piconet 222, for example the DEV 212 and DEV 218, maycommunicate, via RF(k), utilizing an OFDM PHY during the parent CAP 304and/or during assigned time slots within the parent CTA period 308, forexample CTA_2 312 b, . . . , CTA_n−1 312 c and/or CTA_n 312 d. The DEVsmay join the parent piconet 222 during the parent CAP 304 by utilizingan OFDM PHY, for example. The DEVs within the dependent piconet 224, forexample the DEV 214 and DEV 216, may communicate, via RF(k), utilizingan SCM PHY during the dependent CAP 354 and/or during assigned timeslots within the dependent CTA period 358, for example CTA_1 362 a,CTA_2 362 b, . . . , CTA_m−1 362 c and/or CTA_m 362 d. The DEVs may jointhe dependent piconet 224 during the dependent CAP 354 by utilizing anSCM PHY, for example.

In various embodiments of the invention, one or more CTA time slots maybe allocated within the parent CTA period 308 for dependent superframes350 within each parent superframe 300. However, various embodiments ofthe invention may not be so limited. For example, in various otherembodiments of the invention, one or more CTA time slots may beallocated within the parent CTA period 308 for dependent superframes 350within every j^(th) parent superframe 300. For example, in an exemplaryembodiment of the invention in which j=5, one or more CTA time slotswithin the parent CTA period 308 for dependent superframes 350 may beallocated within every 5^(th) parent superframe 300. In variousembodiments of the invention, the dependent beacon frame 352 mayindicate a time instant at which the succeeding dependent superframe maybegin. The time instant indicated within the dependent beacon frame 352may be determined based on the parent superframe time duration, whichmay be indicated within the parent beacon frame 302.

The exemplary dependent superframe 350 comprises a dependent CAP 354.However, in various embodiments of the invention, a dependent superframe350 may or may not comprise a dependent CAP 354. For example, in variousembodiments of the invention, every l^(th) dependent superframe maycomprise a CAP 3rd 354. For example, in an exemplary embodiment of theinvention in which l=3, every dependent superframe 350 may comprise adependent CAP 354. Thus, opportunities to join the dependent piconet 224may occur once in every three dependent superframes 350.

In another exemplary embodiment of the invention, a DEV, for example DEV212, may detect whether a channel, for example channel RF(k), iscurrently being utilized for signal transmissions by other DEVs, forexample DEV 214. The DEV, for example DEV 212, which utilizes a givenPHY, for example an OFDM PHY, may detect signal transmissions by otherDEVs, which utilize OFDM PHYs for signal transmissions. The DEV, forexample DEV 212, may also detect signal energy from signals transmittedby other DEVs. The DEV, for example DEV 212, may also utilize useinformation known about other PHY types to detect signal transmissions,which utilize the other PHY types. The known information may refer tostored information in the DEV. For example, a DEV 212, which utilizes anOFDM PHY, may have known information related to an SCM PHY type. Thus,DEV 212 may utilize the SCM PHY knowledge to detect when another DEV,for example DEV 214, is utilizing RF(k) for signal transmissions. In anexemplary embodiment of the invention, DEV 212 may have knowninformation that enables the DEV 212 to detect preamble information thatis transmitted during SCM PHY signal transmissions, for example.

A DEV, which has been powered on but has not yet joined a piconet may bereferred as making a “cold start”. For example, when powered on, the DEV212 may make a cold start. The cold start DEV 212 may select an RFchannel, which the DEV 212 may utilize for communication with other DEVswithin a piconet. The cold start DEV 212 may either join an existingpiconet, for example piconet 222, or the cold start DEV 212 mayestablish a new piconet. In the latter case, the cold start DEV 212,which utilizes a PHY type, for example an OFDM PHY, may select an RFchannel, RF(f), when no beacon frame transmissions have been detectedvia RF(f) by the cold start DEV 212 for a period of T time units (whereT represents a number of time units, for example, milliseconds), when noframe transmissions utilizing an OFDM PHY for signal transmissions havebeen detected via RF(f) during the period of T time units and when nosignal energy has been detected via RF(f) during the period of T timeunits. When the cold start DEV 212 is able to detect signaltransmissions that utilize other PHY types, for example an SCM PHY, thecold start DEV 212 may also select RF(f) when no frame transmissionshave been detected utilizing an SCM PHY for signal transmissions RF(f)during the period of T time units.

A cold start DEV 212 may join an existing piconet by selecting an RFchannel, for example RF(k), and detecting a beacon frame transmissionsthat utilize a PHY type utilized by the cold start DEV 212. For example,in a cold start DEV 212, which utilizes an OFDM PHY, the cold start DEV212 may detect a transmitted parent beacon 302. In this case, the coldstart DEV 212 may join the parent piconet 222. For a cold start DEV 212,which may utilize a plurality of DEV types, for example an SCM DEV and aOFDM DEV, the cold start DEV 212 may select a preferred PHY type, forexample an SCM PHY, and attempt to detect beacon frame transmissions viaRF(k), which utilize an SCM PHY. In this case, the cold start DEV 212may join the dependent piconet 224.

In various embodiments of the invention, a cold start DEV 212 maydetermine whether to start a new piconet or join an existing piconetbased on a determination of the level of signal traffic that is observedat the cold start DEV 212 for a selected RF channel. For example, thecold start DEV 212 may initially attempt to join the parent piconet 222.In this case, the cold start DEV 212 may select RF(k) and attempt todetermine the level of traffic observed via RF(k). The level of trafficmay be determined based on identified frame transmissions and/or basedon observed signal energy from signal transmissions via RF(k). Ininstances where the level of observed traffic is below a thresholdvalue, T_(thresh), the cold start DEV 212 may attempt to join the parentpiconet 222. In instances where the level of observed traffic is greaterthan or equal to the threshold value T_(thresh), the cold start DEV 212may attempt to start a new piconet. In instances where the cold startDEV 212 utilizes an OFDM PHY but has no knowledge of other PHY types,for example SCM PHYs, the cold start DEV 212 may detect signal energyvia RF(k). The cold start DEV 212 may identify the channel RF(k) asbeing an unusable RF channel. The cold start DEV 212 may select asubsequent RF channel, for example RF(f) and repeat the traffic leveldetermination process.

In various embodiments of the invention in which the PNC 202 utilizes asingle PHY type, or single mode PNC, the PNC 202 may allocate adetermined number of CTA time slots within the parent CTA period 308 byinference. For example, in a single mode PNC, which utilizes an OFDMPHY, the PNC 202 may determine time instants when signal energy isdetected via RF(k), but frame transmissions are not detected. Duringthese time instants, the PNC 202 may determine that signal transmissionsare occurring via RF(k), which utilize a PHY type other than an OFDMPHY, for example an SCM PHY. By detecting starting time instants andending time instants for the detected signal energy via RF(k), the PNC202 may determine time allocations within the parent CTA period 308 forsignal transmission within the dependent piconet 224.

FIG. 4 is a diagram of an exemplary communicating device, which may beutilized in connection with an embodiment of the invention. Referring toFIG. 4, there is shown a transceiver system 400, a receiving antenna 422and a transmitting antenna 432. The transceiver system 400 may beexemplary of the PNC 102 and/or of any of the DEVs 112, 114, 116 and/or118. The transceiver system 400 may comprise at least a receiver 402, atransmitter 404, a processor 406, and a memory 408. Although atransceiver is shown in FIG. 4, transmit and receive functions may beseparately implemented. In various embodiments of the invention, thetransceiver system 400 may comprise a plurality of transmitting antennasand/or a plurality of receiving antennas. Various embodiments of theinvention may comprise a single antenna, which is coupled to thetransmitter 404 and receiver 402 via a transmit and receive switch.

The receiver 402 may comprise suitable logic, circuitry, interfacesand/or code that may be operable to perform receiver functions that maycomprise PHY layer function for the reception or signals. These PHYlayer functions may comprise, but are not limited to, the amplificationof received RF signals, generation of frequency carrier signalscorresponding to selected RF channels, for example uplink or downlinkchannels, the down-conversion of the amplified RF signals by thegenerated frequency carrier signals, demodulation of data contained indata symbols based on application of a selected demodulation type, anddetection of data contained in the demodulated signals. The RF signalsmay be received via the receiving antenna 422. The data may becommunicated to the processor 406.

The transmitter 404 may comprise suitable logic, circuitry, interfacesand/or code that may be operable to perform transmitter functions thatmay comprise PHY layer function for the transmission or signals. ThesePHY layer functions may comprise, but are not limited to, modulation ofreceived data to generate data symbols based on application of aselected modulation type, generation of frequency carrier signalscorresponding to selected RF channels, for example uplink or downlinkchannels, the up-conversion of the data symbols by the generatedfrequency carrier signals, and the generation and amplification of RFsignals. The data may be received from the processor 406. The RF signalsmay be transmitted via the transmitting antenna 432.

The memory 408 may comprise suitable logic, circuitry, interfaces and/orcode that may enable storage and/or retrieval of data and/or code. Thememory 408 may utilize any of a plurality of storage mediumtechnologies, such as volatile memory, for example random access memory(RAM), and/or non-volatile memory, for example electrically erasableprogrammable read only memory (EEPROM). In the context of the presentapplication, the memory 408 may enable storage of code for selection ofa PHY type, for selection of RF channels, for determination of receivedsignal energy, for determination of received frames and fordetermination of time slot allocations. The memory 408 may also beutilized to store known information about a variety of physical layertypes. For example, for a DEV which utilizes an OFDM PHY, the memory 408may be utilized to store known information about other PHY types, suchas SCM PHYs, for example.

In operation, the processor 406 may be operable to enable a PNC 202 togenerate parent beacon frames 302 and dependent beacon frames 352. Theprocessor 406 may be operable to determine CTA time slot assignments forcommunicating devices within a parent piconet 222 and for dependentsuperframes 350. In various embodiments of the invention, the processor406 may be operable to configure the transmitter 404 and/or receiver 402to utilize an SCM PHY and/or an OFDM PHY. The processor 406 may beoperable to enable a PNC 202 and/or a DEV 212 to perform a cold startprocedure. The processor 406 may utilize data and/or code that is storedin the memory 408.

FIG. 5 is a flowchart that illustrates exemplary steps for beacon framegeneration in a piconet controller, in accordance with an embodiment ofthe invention. Referring to FIG. 5, at the start of parent superframe,in step 502, the PNC 202 may determine time allocations forcommunicating DEVs within the parent piconet 222. The PNC 202 maydetermine time allocations for communicating DEVs within the parentpiconet 222 based on CTA time slot requests received during a previousparent superframe. In step 504, the PNC 202 may determine time slotallocations for communicating DEVs within the dependent piconet 224. ThePNC 202 may determine time slot allocations for communicating DEVswithin the dependent piconet based on CTA time slot requests receivedduring a previous dependent superframe and/or based on detected frametransmissions from communicating DEVs within the dependent piconet 224and/or based on signal energy detected when frame transmissions are notdetected. In step 506, the PNC 202 may select a CTA time slot, CTA_1 312a, within the parent CTA period 308 for the dependent superframe 350. Ininstances in which the PNC 202 allocates a CTA time slot for thedependent superframe in every j^(th) parent superframe, the PNC 202 mayselect a CTA time slot for the dependent superframe 350 based on whetherthe current parent superframe is a j^(th) parent superframe. In step510, the PNC 202 may transmit the parent beacon frame 302. The parentbeacon frame 302 may indicate the CTA time slot (if any), which has beenallocated within the parent CTA period 308 for the dependent superframe350. In an exemplary embodiment of the invention, the PNC 202 mayutilize an OFDM PHY to transmit the parent beacon frame 302 via RFchannel RF(k).

In step 512, the PNC 202 may determine whether there is a CTA time slotallocation in the parent CTA period 308 for a dependent superframe 350within the current parent superframe 300. In instances in which there isno allocated parent CTA time slot allocation, for purposes of thepresent figure, the process returns to the start of parent superframenode in anticipation of the succeeding parent superframe 300.

In instances in which it is determined at step 512 that there is anallocated CTA time slot for a dependent superframe 350, in step 514, thePNC 202 may determine whether the beginning time instant for theassigned CTA time slot, CTA_1 312 a, has arrived. In instances in whichthe beginning time instant has not arrived, for purposes of the presentfigure, the process waits at step 514.

In instances in which it is determined at step 514 that the beginningtime instant for the CTA_1 312 a time slot has arrived, in step 516, thePNC 202 may determine whether the present dependent superframe 350comprises a dependent CAP 354. In instances in which the PNC 202allocates a dependent CAP 354 in every l^(th) dependent superframe, thePNC 202 may make the determination based on whether the currentdependent superframe is an l^(th) dependent superframe. In instances inwhich the PNC 202 determines that no dependent CAP is to be allocated inthe current dependent superframe, in step 518, the PNC 202 may indicatein a dependent beacon frame that the current dependent superframe doesnot comprise a dependent CAP 354.

In instances in which it is determined at step 516 that there is adependent CAP 354 in the current dependent superframe, the PNC 202 mayindicate in a dependent beacon frame that the current dependentsuperframe comprises a dependent CAP 354. In step 522, the PNC 202 maytransmit the dependent beacon frame 352. In an exemplary embodiment ofthe invention, the PNC 202 may utilize an SCM PHY to transmit thedependent beacon frame 352 via RF channel RF(k).

FIG. 6 is a flowchart that illustrates exemplary steps for cold startoperation of a communicating device, in accordance with an embodiment ofthe invention. The flowchart presented in FIG. 6 illustrates exemplarysteps for a DEV 114 or DEV 116 within a dependent piconet 224, but thecold start procedure presented in FIG. 6 may be similarly applied for aDEV 112 or DEV 118 within a parent piconet 222. Referring to FIG. 6,after a cold start DEV has been powered on, in step 602, the cold startDEV may initialize an RF channel index, k=1. For purposes of the currentfigure, the RF channel index may be utilized as an index for selectionof an RF channel. In step 604, the cold start DEV may select an RFchannel, RF(k), based on the current RF channel index value k. In step606, the cold start DEV may select an SCM PHY type. The selected PHYtype may be utilized by the cold start DEV for transmission and/orreception of signals. In step 608, the cold start DEV may start a timer.The timer may determine the time duration for the cold start process. Instep 610, the cold start DEV may determine whether a beacon frametransmission has been detected. In instances in which a beacon frametransmission has been detected in step 610, in step 612, the cold startDEV may join an existing piconet [RF(k),SCM]. The cold start DEV mayestablish an association with the existing piconet by joining theexisting piconet. The cold start DEV may join an existing piconet bycommunicating with a coordinating communication DEV, such as a PNC 202,which are currently associated with the existing piconet. Joining theexisting piconet may enable the cold start DEV to communicate with othercommunicating DEVs and/or coordinating communication DEVs that areassociated with the existing piconet. These DEVs may be referred to asbeing members of the existing piconet. When communicating with otherDEVs that are members of the existing piconet, the cold start DEV mayutilize RF channel RF(k) and an SCM PHY type.

In instances in which a beacon frame transmission has not been detectedin step 610, in step 614, the cold start DEV may determine whether frametransmission utilizing an OFDM PHY has been detected. The cold start DEVmay determine that a frame transmission has occurred via RF(k) utilizingan OFDM PHY based on known information at the cold start DEV, which isrelated to OFDM PHY signal transmission. In step 614, the cold start DEVmay also determine whether signal energy has been detected even thoughno frame transmission has been detected. In this case, the cold startDEV may detect signal energy but may not be able to determine the PHYtype utilized for the signal transmission. In instances in which a coldstart DEV has detected OFDM PHY frame transmission or has detectedsignal energy without detecting frame transmission in step 614, in step616, the cold start DEV may modify the RF channel index k. The RFchannel index modification may enable the cold start DEV to select a newRF channel. Step 604 may follow step 614.

In instances in which a cold start DEV has not detected OFDM PHY frametransmission nor has detected signal energy without detecting frametransmission in step 614, in step 618, the cold start DEV may determinewhether T time units has elapsed since the start of the time in step608. In instances in which T time units has not elapsed in step 618,step 610 may follow step 618. In instances in which T time units haselapsed in step 618, in step 620, the cold start DEV may start a newpiconet [RF(k),SCM]. The cold start DEV may start the new piconet bytransmitting an originating beacon frame via a selected RF(k) channel.The cold start DEV may also perform a coordinating communication DEVrole in the new piconet. Communicating devices, which join the newpiconet may utilize RF channel RF(k) and an SCM PHY type.

In various embodiments of the invention, a frame may be referred to as aprotocol data unit (PDU). An exemplary PDU is a beacon frame. Othertypes of frames, packets and/or messages may also be referred to asPDUs. For example, data communications between communicating DEVs withina piconet may involve the transmission of PDUs from an originating DEVto a destination DEV. The transmitted PDUs may comprise the data beingtransferred during the data communications between the communicatingDEVs.

In various embodiments of the invention, a piconet may be referred to asa network. For example, a parent piconet may be referred to as a parentnetwork while a dependent piconet may be referred to as a dependentnetwork. Thus, various embodiments of the invention may not be limitedto communications between communicating devices within a piconet, butembodiments of the invention may also be practiced between communicatingdevices in a variety of networks, such as wireless local area networks(WLAN), for example.

Another embodiment of the invention may provide a machine and/orcomputer readable medium, having stored thereon, a computer programhaving at least one code section executable by a machine and/orcomputer, thereby causing the machine and/or computer to perform thesteps as described herein for dual mode operation in wireless networks.

Various embodiments of the invention may comprise a method and systemfor generating contents of protocol data units (PDUs), which aretransmitted by communicating DEVs. The contents of the PDUs may betransmitted via signals, which may collectively be referred to as a“burst”.

FIG. 7 is a diagram of an exemplary protocol data unit, which may beutilized in connection with an embodiment of the invention. Referring toFIG. 7, there is shown a PDU 700. The PDU 700 may comprise a shortsequence field 702, a long sequence field 704, a header field 706 and apayload field 708. In various embodiments of the invention, the PDU 700format may be specified in a physical (PHY) layer specification, forexample such as a PHY level specification for IEEE 802.11 wireless LANsystems.

In IEEE 802.11 WLAN systems, the short sequence field 702 may bereferred to as short training sequence and the long sequence field 704may be referred to as a long training sequence. A preamble field maycomprise the short training sequence and the long training sequence. Theheader field 706 may comprise a SIGNAL field.

The short sequence field 702 may enable signal detection and automaticgain control (AGC) level setting at a receiving DEV. Signal detection,also referred to as burst acquisition, may enable the receiving DEV todetermine the presence of transmitted signal energy in a communicationmedium. AGC level setting may enable a receiver 402 to set a gain levelfor amplification of received signals. The short sequence field 702 mayalso enable course frequency tuning and timing synchronization at thereceiving DEV. The course frequency tuning and timing synchronizationmay enable the receiving DEV to determine an approximate frequency forthe received signal and to synchronize an internal clock to receive datacontained in the received PDU.

The long sequence field 704 may enable fine frequency tuning at thereceiving DEV. The fine frequency turning may enable the receiving DEVto determine an RF channel that is to be utilized for receipt ofsignals.

The header field 706 may comprise information that specifies the lengthof the payload field 708, for example as measured in units of octets.The header field 706 may also comprise a modulation and coding scheme(MCS) field, which identifies a modulation type and/or coding typeutilized for encoding data within the payload field 708.

The payload field 708 may comprise data that are to be received and/orprocessed by the receiving DEV. The data contained within the payloadfield 708 may be encoded based on an MCS as specified in the headerfield 706. The payload field 708 may also comprise data that has beenencoded utilizing an inner and/or outer forward error correction (FEC)coding scheme.

The short sequence field 702, long sequence field 704, header field 706and/or payload field 708 may be received at the receiving DEV viasignals that are transmitted via a communication medium and received viaa receiving antenna 422. The signals received via the receiving antenna422 may be processed by a receiver 402. The receiver 402 may perform PHYlayer processing on the received signal to decode the signals andgenerate bits, which correspond to the short sequence field 702, longsequence field 704, header field 706 and/or payload field 708,respectively. For example, the receiver 402 may receive a plurality ofsignal levels at various time instants. In an exemplary embodiment ofthe invention, each of the received signal levels may correspond to achip. In other embodiments of the invention, each of the received signallevels may correspond to a symbol.

In instances, in which each of the received signal levels corresponds toa chip, the receiver 402 may utilize a despreading algorithm, whichconverts a plurality of chips to a corresponding symbol. The number ofchips, which correspond to a single symbol, may be determined based on aspreading factor.

In instances, in which each of the received signal levels corresponds toa symbol, the receiver 402 may utilize a constellation map to converteach symbol into one or more bits. The constellation map may bedetermined based on a modulation type. The number of bits, whichcorrespond to a single symbol, may be determined based on the modulationtype.

In various embodiments of the invention, a π/2-BPSK (binary phase shiftkeying) modulation type may be utilized by the receiver 402 for PHYlayer processing of signals, which correspond to one or more of theshort sequence field 702, long sequence field 704, the header field 706and/or the payload field 708. In various embodiments of the invention, atransmitter 404 may receive a plurality of input bits, b_(in,m), where mrepresents an m^(th) bit among the plurality of bits. Based on the bits,b_(in,m), symbols may be generated at the transmitter 404 utilizingπ/2-BPSK by generating a plurality of symbols utilizing BPSK, s_(in,k),where k represents a k^(th) symbol among the plurality of symbols andphase shifting each successive BPSK symbol, s_(in,k), by a phaserotation of π/2. The plurality of π/2-BPSK symbols, s_(out,k), may berepresented as shown in the following equation:s _(out,k) =s _(in,k) *e ^(j*π*k/2)  [1]where j=√{square root over (−1)} and k=0,1, . . . . In instances, whereBPSK modulation is utilized, the number of symbols, s_(in,k), may beequal to the number of bits, b_(in,m).

The receiver 402, which receives signals comprising π/2-BPSK symbols,may generate a plurality of output bits, b_(out,m), based on equation[1] and the constellation map for the BPSK modulation type. The outputbits, b_(out,m), generated at the receiver 402 may comprise estimatedvalues for the input bits, b_(in,m), generated at the transmitter 404 asrepresented in the following equation:b _(out,m) ={circumflex over (b)} _(in,m)  [2]

FIG. 8 is a block diagram of an exemplary transmitter, in accordancewith an embodiment of the invention. Referring to FIG. 8, there is showna transmitter 800. The transmitter 800 may comprise a mapper 802, a chiprotation block 804, a filter block 806 and a quadrature modulator 808.In an exemplary embodiment of the invention, the mapper 802 may receivea plurality of input bits, b_(in,m). The mapper 802 may comprisesuitable logic, circuitry and/or code that are operable to utilize aBPSK modulation type to generate a plurality of symbols, s_(in,k). Thechip rotation block 804 may comprise suitable logic circuitry and/orcode that are operable to receive the plurality of symbols, s_(in,k),and generate a corresponding plurality of phase rotated symbols,s_(out,k), as represented in equation [1]. The chip rotation block 804may utilize a spreading algorithm to generate a plurality of chips basedon each phase rotated symbol, s_(out,k). In an exemplary embodiment ofthe invention, the filter block 806 may comprise suitable logic,circuitry and/or code that are operable to perform low pass filtering onthe output signal from the chip rotation block 804. The filter block 806may output a filtered signal, which is input to the quadrature modulator808. The quadrature modulator 808 may comprise suitable logic, circuitryand/or code as may commonly be found in quadrature modulator circuits.

In various embodiments of the invention, the mapper 802 may utilizeother modulation types. For example, in an exemplary embodiment of theinvention, the mapper 802 may utilize quaternary phase shift keying(QPSK) when generating symbols.

In an exemplary embodiment of the invention, the short sequence field702 may comprise a repeated chip sequence. The chip sequence maycomprise a 128-chip Golay code sequence, c_(n), where n indicates adistinct 128-chip Golay code sequence among a plurality of N distinctGolay code sequences. In an exemplary embodiment of the invention, N=4.Correspondingly, there may be four distinct Golay code sequences: c₀,c₁, c₂ and c₃. In an exemplary embodiment of the invention, chips withineach Golay code sequence may be encoded utilizing a π/2-BPSKconstellation map.

In various embodiments the invention, communicating DEVs within a givenpiconet may select distinct Golay code sequence, c_(n). The selectedGolay code sequence may then be utilized in a repeated sequence withinthe short sequence field 702 for PDUs transmitted within the piconet.For example, communicating DEVs within the parent piconet 222 mayutilize Golay code sequence c₀ while communicating DEVs within thedependent piconet 224 may utilize Golay code sequence c₁. Thus, PDUstransmitted by DEV 212 may comprise a short sequence field 702, whichcomprises a repeated chip sequence based on Golay code sequence c₀,while PDUs transmitted by DEV 214 may comprise a short sequence field702, which comprises a repeated chip sequence based on Golay codesequence c_(1.)

In various embodiments of the invention, the number of repetitions ofthe selected Golay code sequence may be determined based on a length ofthe short sequence field 702. In an exemplary short length version ofthe short sequence field 702, the selected Golay code sequence, c_(n),may be repeated eight times, wherein the last two repetitions maycomprise a negated version of the Golay code sequence, −c_(n), as shownbelow:Short_Sequence_Field(Short)=c _(n) ,c _(n) ,c _(n) ,c _(n) ,c _(n) ,c_(n) ,−c _(n) ,−c _(n)  [3]where −c_(n) may represent a two's complement representation, or one'scomplement representation, of c_(n).

In an exemplary medium length version of the short sequence field 702,the selected Golay code sequence, c_(n), may be repeated sixteen times,wherein the last four repetitions may comprise −c_(n). In an exemplarylong length version of the short sequence field 702, c_(n) may berepeated forty times, wherein the last eight repetitions may comprise−c_(n).

In an exemplary embodiment of the invention, the long sequence field 704may comprise a pair of complementary Golay code sequences: Seq_a, Seq_b.Each of the Golay code sequences, Seq_a and Seq_b, may comprise a512-chip Golay code sequence, wherein the 512-chip Golay code sequence,Seq_a, is a complementary to the 512-chip Golay code sequence, Seq_b. Inan exemplary embodiment of the invention, chips within each Golay codesequence, Seq_a, Seq_b, may be encoded utilizing a π/2-BPSKconstellation map. In another exemplary embodiment of the invention,chips within each Golay code sequence, Seq_a, Seq_b, may be encodedutilizing a BPSK constellation map. In various other embodiments of theinvention, other constellation maps may be utilized, for example, QPSKand/or π/2-QPSK.

In an exemplary embodiment of the invention, a long sequence field 704may be represented as shown below:Long_Sequence_Field=G,a _(384, . . . ,511),Seq_(—) a,G,b_(384, . . . ,511),Seq_(—) b  [4]where a_(384, . . . , 511) represents a 128-chip cyclic prefix thatprecedes Golay code sequence Seq_a and b_(384, . . . , 511) represents a128-chip cyclic prefix that precedes Golay code sequence Seq_b and Grepresents a guard interval.

In various embodiments of the invention, the long sequence field 704 maycomprise repeated Golay code sequences Seq_a and Seq_b as shown below:Long_Sequence_Field=a _(384, . . . ,511),Seq_(—) a, . . . ,Seq _(—) a,b_(384, . . . ,511),Seq_(—) b, . . . ,Seq _(—) b  [5]

The receiver 402, which receives PDUs, may utilize a received longsequence field 704 to compute channel estimate values, ĥ_(n). Thecomputed channel estimate values may characterize the communicationmedium through which the received signals have propagated. Based on thecomputed channel estimate values, the receiver may compute estimated bitvalues,{circumflex over (b)}_(in,m), for data bits in the payload field708.

Signals received at the receiver 402 during the long sequence field 704portion of the received PDU 700 may comprise a plurality of chips. Aportion of the received chips may correspond to chip sequences Seq_a andSeq_b respectively. The chips corresponding to Seq_a may be referred toas a_(k), while the chips corresponding to Seq_b may be referred to asb_(k). A plurality of symbol values, x_(k), may be computed based on thereceived chips from sequences Seq_a and Seq_b respectively as shown inthe following equation:

$\begin{matrix}{x_{k} = {{\sum\limits_{n = 0}^{\upsilon}{h_{n} \cdot c_{k - n}}} + n_{k}}} & \lbrack 6\rbrack\end{matrix}$where h_(n)·c_(k-n) represents values in a received chip sequence, c_(k)represents the corresponding values in a chip sequence (for example,c_(k)=a_(k) or sequence c_(k)=b_(k)) at the transmitter, h_(n)represents the impulse response of the communication medium (the valueof which is estimated by the channel estimate ĥ_(n)), n_(k) representschannel noise and υ represents the number of chips that correspond to asymbol.

The values of the received chips may differ in relation to thecorresponding chip values in the sequences, a_(k) and b_(k), based onchannel impulse response values h_(n). These differences result from thepropagation of the signals across the communication medium and representa form of signal distortion referred to as fading. Fading may result inmagnitude and/or phase distortion in transmitted signals. Since the chipsequences a_(k) and b_(k) are typically known among communicating DEVswithin a given piconet, the receiver 402 may compute channel estimatevalues, ĥ_(n) based on the known chip sequence, a_(k), the known chipsequence, b_(k), and the values of the received chips.

In an exemplary embodiment of the invention, for a Golay sequence a_(k),computed symbol values x_(k) may be determined as shown in the followingequation:

$\begin{matrix}{{x_{k} = {{\sum\limits_{n = 0}^{\upsilon}{h_{n} \cdot a_{{({k - L_{guard} - n})}{mod}\; L}}} + n_{k}}},{{{for}\mspace{14mu} k} = L_{guard}},K,{L_{guard} + L - 1}} & \lbrack 7\rbrack\end{matrix}$where L_(guard) represents a duration for a guard interval (for examplethe guard interval may represent the length of the cyclic prefixa_(384 . . . 511)), L represents the number of points in a discreteFourier transform (DFT) algorithm. In equation [7], the index for chipsa_(k) is computed for a modulus base of L_(guard). In an exemplaryembodiment of the invention, L=512.

For a Golay sequence Seq_b, computed values x_(k) may be determined asshown in the following equation:

$\begin{matrix}{{x_{k} = {{\sum\limits_{n = 0}^{\upsilon}{h_{n} \cdot b_{{({k - {2 \cdot L_{guard}} - n})}{mod}\; L}}} + n_{k}}},{{{for}\mspace{14mu} k} = {{2 \cdot L_{guard}} + L}},K,{{2 \cdot \left( {L_{guard} + L} \right)} - 1}} & \lbrack 8\rbrack\end{matrix}$

Based on the computed symbol values x_(k) in equations [7] and [8],corresponding L-point DFT values may be computed respectively as shownin the following equations:

$\begin{matrix}{X_{0,m} = {\sum\limits_{k = L_{guard}}^{L_{guard} + L - 1}{x_{k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \frac{2 \cdot \pi \cdot {({k - L_{guard}})}}{L}}}}} & \lbrack 9\rbrack \\{X_{1,m} = {\sum\limits_{k = {{2 \cdot L_{guard}} + L}}^{{2 \cdot {({L_{guard} + L})}} - 1}{x_{k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \frac{2 \cdot \pi \cdot {({k - {2 \cdot L_{guard}} - L})}}{L}}}}} & \lbrack 10\rbrack\end{matrix}$

Based on the chip sequences, a_(k) and b_(k), corresponding L-point DFTvalues may be computed respectively as shown in the following equations:

$\begin{matrix}{A_{m}^{\%} = {\sum\limits_{k = 0}^{L - 1}{a_{L - k - 1} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \frac{2 \cdot \pi \cdot k}{L}}}}} & \lbrack 11\rbrack \\{B_{m}^{\%} = {\sum\limits_{k = 0}^{L - 1}{b_{L - k - 1} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \frac{2 \cdot \pi \cdot k}{L}}}}} & \lbrack 12\rbrack\end{matrix}$

The properties of the Golay chip sequences, a_(k) and b_(k), may becharacterized as shown in the following equations:

$\begin{matrix}{{\rho_{a}(k)} = {\sum\limits_{n = 0}^{L - k - 1}{a_{n} \cdot a_{n + k}}}} & \left\lbrack {13a} \right\rbrack \\{{\rho_{b}(k)} = {\sum\limits_{n = 0}^{L - k - 1}{b_{n} \cdot b_{n + k}}}} & \left\lbrack {13b} \right\rbrack \\{{{\rho_{a}(k)} + {\rho_{b}(k)}} = \left\{ \begin{matrix}{0,{k = {{1\mspace{14mu}\ldots\mspace{14mu} L} - 1}}} \\{{2 \cdot L},{k = 0}}\end{matrix} \right.} & \left\lbrack {13c} \right\rbrack\end{matrix}$

Based on the DFT values computed in equations [9]-[12] a correlationvalue may be computed as shown in the following equation:

$\begin{matrix}{{\hat{H}}_{m} = \frac{{X_{0,m} \cdot A_{m}^{\%}} + {X_{1,m} \cdot B_{m}^{\%}}}{2 \cdot L}} & \lbrack 14\rbrack\end{matrix}$Channel estimate values, ĥ_(n), may be computed based on L-point DFTvalues computed from the correlation values Ĥ_(m) as shown in thefollowing equation:

$\begin{matrix}{{\hat{h}}_{n} = {\sum\limits_{m = 0}^{L - 1}{{\hat{H}}_{m} \cdot {\mathbb{e}}^{{- {\mathbb{i}}} \cdot \frac{2 \cdot \pi \cdot m}{L}}}}} & \lbrack 15\rbrack\end{matrix}$

In various embodiments of the invention, symbols within the header field706 may be encoded based on any of a plurality of modulation types, forexample, BPSK, π/2-BPSK, QPSK or π/2-QPSK. The header field 706 may alsocomprise a guard interval. In an exemplary embodiment of the invention,the guard interval within the header field 706 may comprise 64 chips. Inan exemplary embodiment of the invention, the symbols within the headerfield 706 may be generated based on encoded bits. The encoded bits maybe encoded based on inner forward error correction coding (FEC), forexample. In an exemplary embodiment of the invention, the inner FEC maybe based on low density parity check (LDPC) coding. The coding rate, r,for the LDPC may be represented r=½. In various embodiments of theinvention, chips may be generated based on the symbols based on aspreading factor of 2 times (2×) or 4 times (4×), for example.

In various embodiments of the invention, the header field 706 maycomprise a Length field. The Length field may comprise a plurality ofbits, for example 20 bits, which indicate the length of at least aportion of the PDU 700. In an exemplary embodiment of the invention, theLength field indicates the length of the payload field 708. The Lengthfield may indicate the PDU length in units of octets, for example. Theheader field 706 may comprise an MCS field, which indicates themodulation and coding scheme (MCS), which is utilized for encoding atleast a portion of the bits in the PDU 700. The MCS field may comprise aplurality of bits, for example, 8 bits, which indicates a modulationtype and/or coding rate, which is utilized for encoding bits in thepayload field 708. In an exemplary embodiment of the invention, the MCSfield may indicate when at least a portion of the bits within the PDU700 are encoded and transmitted utilizing π/2-BPSK and single carriermodulation (SCM), when at least a portion of the bits within the PDU 700are encoded and transmitted utilizing BPSK and SCM or when at least aportion of the bits within the PDU 700 are encoded and transmittedutilizing orthogonal frequency division multiplexing (OFDM), forexample.

The header field 706 may comprise a guard interval duration field, whichindicates the length, in units of chips, for example, for a guardinterval. In an exemplary embodiment of the invention, the guardinterval duration field may comprise a single bit. Notwithstanding, theinvention is not so limited, and one or more bits may be utilized tospecify the guard interval duration.

The header field 706 may comprise a number of spatial streams (NSS)field, which indicates the number of spatial streams utilized by atransmitting DEV. In various embodiments of the invention, the NSS fieldmay be utilized in connection with multiple input, multiple output(MIMO) communication systems. In an exemplary embodiment of theinvention, the NSS field may comprise 2 bits. Notwithstanding, theinvention is not so limited, and one or more bits may be utilized tospecify the number of spatial streams utilized by a transmitting DEV.

The header field 706 may comprise a preamble type field. In variousembodiments of the invention, the preamble type field may indicate thelength of the short sequence field 702 portion of the PDU. In anexemplary embodiment of the invention, the preamble type field maycomprise 2 or more bits. In various exemplary embodiments of theinvention, one distinct 2-bit value may indicate that the succeeding PDU700 may comprise a short length version of the short sequence field 702,another distinct 2-bit value may indicate that the succeeding PDU 700may comprise a medium length version of the short sequence field 702 andanother distinct 2-bit value may indicate that the succeeding PDU 700may comprise a long length version of the short sequence field 702.

The header field 706 may comprise an aggregation field, a scramblerinitialization field, a header check sequence field and various reservedbits. Each of these fields may operate substantially as described invarious communication standards documents, such as in one or more IEEE802 specifications, for example.

In various embodiments of the invention, symbols within the payloadfield 708 may be encoded based on any of a plurality of modulationtypes, for example, BPSK, π/2-BPSK, QPSK, π/2-QPSK or OFDM. The payloadfield 708 may also comprise one or more guard intervals. In an exemplaryembodiment of the invention, the guard interval(s) within the payloadfield 708 may comprise 64 chips. In an exemplary embodiment of theinvention, the symbols within the payload field 708 may be generatedbased on encoded bits. The encoded bits may be encoded based on an innerFEC as specified in the preceding header field 706, for example. Invarious embodiments of the invention, chips may be generated based onthe symbols based on a spreading factor of 4 times (4×), 16 times (16×)or 64 times (64×), for example. Symbols generated in connection withOFDM, for example, may utilize frequency interleaving and/or spatialinterleaving.

FIG. 9 is a block diagram of an exemplary single mode transmitter, inaccordance with an embodiment of the invention. Referring to FIG. 9, inan exemplary embodiment of the invention, the single mode transmitter900 may be utilized in a single mode DEV, which utilizes an SCM PHY, forexample DEV 114. The single mode transmitter 900 may comprise a preambleand header encoder block 902, a scrambling and inner coding block 904, amultiplexer (MUX) 906, a mapper 908, a spreading and chip rotation block910, a prefix insertion block 912, a filter block 914 and a quadraturemodulator 916.

The preamble and header encoder block 902 may comprise suitable logic,circuitry and/or code that are operable to receive input header bits andgenerate bits for a short sequence field 702, long sequence field 704and header field 706. The input header bits may be utilized forgeneration of bits for the header field 706.

The scrambling and inner coding block 904 may comprise suitable logic,circuitry and/or code that are operable to receive input payload bitsand generate bits for a payload field 708. The MUX 906 may comprisesuitable logic, circuitry and/or code that are operable to receive inputfrom the preamble and header encoder block 902 and from the scramblingand inner coding block 904 and selectively output bits for the shortsequence field 702, long sequence field 704, header field 706 andpayload field 708. The mapper 908 is substantially similar to the mapper802. In an exemplary embodiment of the invention, the mapper 908 mayutilize a BPSK modulation type with SCM, a π/2-BPSK modulation type withSCM, a QPSK modulation type with SCM or a π/2-QPSK modulation type withSCM, for example. The spreading and chip rotation block 910 issubstantially similar to the chip rotation block 804.

The prefix insertion block 912 may comprise suitable logic, circuitryand/or code that are operable to generate chips for one or moregenerated guard intervals. The prefix insertion block 912 may insert thegenerate guard intervals at specified locations within the shortsequence field 702, long sequence field 704, header field 706 and/orpayload field 708. The filter block 914 is substantially similar to thefilter 806. The quadrature modulator 916 is substantially similar to thequadrature modulator 808.

In operation, the preamble and header encoder block 902 may receiveinput bits for the preamble and/or header portion of a PDU 700. Theinput bits for the preamble and/or header portion of the PDU 700 may bereceived from a processor 406 and/or from a memory 408. The preamble andheader encoder block 902 may generate a short sequence field 702, longsequence field 704 and/or header 706 as described above. The scramblingand inner coding block 904 may receive input bits for the payloadportion of the PDU 700. The input bits for the payload portion of thePDU may be received from a processor 406 and/or from a memory 408. Thescrambling and inner coding block 904 may generate a payload field 708as described above.

The MUX 906 may selectively output an input received from the preambleand header encoder block 902 or an input received from the scramblingand inner coding block 904. The MUX 906 may select an input receivedfrom the preamble and header encoder block 902 at time instants thatcorrespond to the short sequence 702, long sequence 704 and/or header706 portions of a PDU 700. The MUX 906 may select an input received fromthe scrambling and inner coding block 904 at time instants thatcorrespond to the payload 708 portion of a PDU 700. The MUX 906 may makea selection based on a signal from, for example, the processor 406.

The mapper 908 may receive input from the MUX 906 and output symbols asdescribed above. The spreading and chip rotation block 910 may receivesymbols from the mapper 906 and output chips as described above. Theprefix insertion block 912 may receive chips from the spreading and chiprotation block 910 and insert one or more guard intervals as describedabove. The filter 914 may filter a signal received from the prefixinsertion 912 block and output a filtered signal as described above. Thequadrature modulator 916 may receive a filtered signal from the filter914 and generate signals for transmission as described above. Thesignals may be transmitted via a transmitting antenna 432, for example.

FIG. 10 is a block diagram of an exemplary dual mode transmitter, inaccordance with an embodiment of the invention. Referring to FIG. 10, inan exemplary embodiment of the invention, the dual mode transmitter 1000may be utilized in a dual mode DEV, which utilizes an SCM PHY and/or anOFDM PHY, for example DEV 112. The dual mode transmitter 1000 maycomprise a preamble and header encoder block 902, a scrambling and innercoding block 904, a multiplexer (MUX) 906, an SCM mapper 1008, aspreading and chip rotation block 910, an OFDM mapper 1018, aninterleaver 1020, and inverse fast Fourier transform (IFFT) block 1022,a MUX 1024, a prefix insertion block 1012, a filter block 1014 and aquadrature modulator 1016.

The preamble and header encoder block 902, scrambling and inner codingblock 904, MUX 906 and spreading and chip rotation block 910 may besubstantially as described above for FIG. 9. The prefix insertion block1012 may be substantially similar to the prefix insertion block 912. Thefilter block 1014 is substantially similar to the filter block 914. Thequadrature modulator block 1016 may be substantially similar to thequadrature modulator block 916. The SCM mapper 1008 may be substantiallysimilar to the SCM mapper 908. In an exemplary embodiment of theinvention, the SCM mapper 1008 may utilize a BPSK modulation type withSCM, a π/2-BPSK modulation type with SCM, a QPSK modulation type withSCM or a π/2-QPSK modulation type with SCM, for example.

The OFDM mapper 1018 may comprise suitable logic, circuitry and/or codethat are operable to receive bits from the scrambling and inner codingblock 904 and generate symbols. In various embodiments of the invention,the OFDM mapper 1018 may perform bit interleaving on the bits receivedfrom the scrambling and inner coding block 904 prior to generation ofthe symbols. In connection with the generation of symbols, the OFDMmapper 1018 may utilize a quadrature amplitude modulation (QAM)modulation type with OFDM, for example. The OFDM mapper 1018 may beoperable to generate individual symbols in an order that associates theindividual symbols with one or more carrier frequencies selected fromwithin an OFDM channel bandwidth.

The interleaver 1020 may comprise suitable logic, circuitry and/or codethat are operable to perform frequency and/or spatial interleaving onsymbols received from the OFDM mapper 1018. In an exemplary embodimentof the invention, the interleaver 1020 may be operable to rearrange theorder of the symbols received from the OFDM mapper 1018.

The IFFT 1022 block may comprise suitable logic, circuitry and/or codethat may be operable to receive a frequency domain representation ofsymbols from the interleaver 1020 and generate a time domainrepresentation of the symbols.

The MUX 1024 may comprise suitable logic, circuitry and/or code that mayenable the MUX 1024 to receive input from the spreading and chiprotation block 910 and the IFFT block 1022. The MUX 1024 may enable thedual mode transmitter 1000 to transmit signals utilizing an SCM PHY byselectively outputting a signal, which is input from the spreading andchip rotation block 910. The MUX 1024 may enable the dual modetransmitter 1000 to transmit signals utilizing an OFDM PHY byselectively outputting a signal, which is input from the IFFT block1022.

In operation, the preamble and header encoder block 902 may receiveinput bits for the preamble and/or header portion of a PDU 700. Theinput bits for the preamble and/or header portion of the PDU 700 may bereceived from a processor 406 and/or from a memory 408. The preamble andheader encoder block 902 may generate a short sequence field 702, longsequence field 704 and/or header 706 as described above. The scramblingand inner coding block 904 may receive input bits for the payloadportion of the PDU 700. The input bits for the payload portion of thePDU may be received from a processor 406 and/or from a memory 408. Thescrambling and inner coding block 904 may generate a payload field 708as described above.

The MUX 906 may selectively output an input received from the preambleand header encoder block 902 or an input received from the scramblingand inner coding block 904. The MUX 906 may select an input receivedfrom the preamble and header encoder block 902 at time instants thatcorrespond to the short sequence 702, long sequence 704 and/or header706 portions of a PDU 700. The MUX 906 may select an input received fromthe scrambling and inner coding block 904 at time instants thatcorrespond to the payload 708 portion of a PDU 700. The MUX 906 may makea selection based on a signal from, for example, the processor 406.

The SCM mapper 1008 may receive input from the MUX 906 and outputsymbols as described above. The spreading and chip rotation block 910may receive symbols from the SCM mapper 1006 and output chips asdescribed above. The OFDM mapper 1018 may receive input from thescrambling and inner coding block 904 and output symbols as describedabove. The interleaver 1020 may receive symbols in a frequency sequencefrom the ODFM mapper 1018 and output a frequency domain signal afterrearranging the frequency sequence order of the symbols received fromthe OFDM mapper 1018 as described above. The IFFT 1022 may receive thefrequency domain signal output from the interleaver 1020 and generate atime domain signal as described above.

The MUX 1024 may selectively output an input received from the spreadingand chip rotation block 910 or an input received from the IFFT block1022. The MUX 1024 may make a selection based on a signal from, forexample, the processor 406. The prefix insertion block 1012 may receivean input signal from the MUX 1024 and insert one or more guard intervalsas described above. The filter 1014 may filter a signal received fromthe prefix insertion 1012 block and output a filtered signal asdescribed above. The quadrature modulator 1016 may receive a filteredsignal from the filter 1014 and generate signals for transmission asdescribed above.

FIG. 11 is a block diagram of an exemplary dual mode receiver, inaccordance with an embodiment of the invention. Referring to FIG. 11, inan exemplary embodiment of the invention, the dual mode receiver 1100may be utilized in a dual mode DEV, which utilizes an SCM PHY and/or anOFDM PHY, for example DEV 112. The dual mode receiver 1100 may comprisea preamble detection and channel estimation block 1102, a header decoderblock 1104, a prefix removal block 1106, a fast Fourier transform (FFT)block 1108, an equalization block 1110, an IFFT block 1112, and are-sampler and filter block 1114. The dual mode receiver 1100 may alsocomprise an SCM de-mapper block 116, an OFDM de-mapper block 1118, ade-interleaver block 1120, a MUX 1122 and an inner de-coding andde-scrambling block 1124. The IFFT block 1112 is substantially similarto the IFFT block 1022.

The preamble detection and channel estimation block 1102 may comprisesuitable logic, circuitry and/or code that are operable to receive andprocess chips from the short sequence field 702 and long sequence field704 portions of a PDU 700. During processing of the short sequence fieldand/or long sequence field 704, the preamble detection and channelestimation block 1102 may compute channel estimate values ĥ_(n).

The header decoder block 1104 may comprise suitable logic, circuitryand/or code that are operable to receive and process chips from theheader field 706 portion of a PDU 700. During processing of the headerfield, the header decoding block 1104 may determine a modulation typeand inner coding type, which are to be utilized during processing of thepayload field 708 portion of the PDU 700.

The prefix removal block 1106 may comprise suitable logic, circuitryand/or code that are operable to remove guard intervals that wereinserted into the PDU 700 by the prefix insertion block 1012 at atransmitter 1000.

The FFT 1108 may comprise suitable logic, circuitry and/or code that areoperable to receive a time domain signal and generate a frequency domainrepresentation of the received signal. The frequency domainrepresentation of the received signal may enable identification of eachcarrier frequency component within the received time domain signal. TheFFT 1108 may also be operable to perform despreading of chips in thereceived time domain signal such that the frequency domainrepresentation of the received signal comprises symbols.

The equalization block 1110 may comprise suitable logic, circuitryand/or code that are operable to generate output signals that compriseadjusted signal levels from the received signal. The equalization block1110 may be operable to adjust signal levels to compensate for fading.The compensation may be referred to as signal equalization. Theequalization block 1110 may utilize computed channel estimates, ĥ_(n),during signal equalization.

The re-sampler and filter block 1114 may comprise suitable logic,circuitry and/or code that are operable to sample a time domain signalat a determined sampling rate. The sampled signal may be filtered in amanner, which may be substantially similar to that described for thefilter 806. In an exemplary embodiment of the invention, the determinedsampling rate may be equal to

$\frac{3}{2*T},$where T refers to a symbol time duration.

The SCM de-mapper block 1116 may comprise suitable logic, circuitryand/or code that are operable to receive individual symbols and generateone or more bits from each received symbol. The SCM de-mapper block 1116may be operable to receive an input that identifies a modulation type.The modulation type may enable the SCM de-mapper block 1116 to select aconstellation map. Upon receipt of each symbol, the SCM de-mapper 1116may identify a corresponding point in the constellation map and generatethe corresponding bits. In various embodiments of the invention, the SCMde-mapper 1116 may receive symbols from a signal, which comprises asingle carrier frequency.

The OFDM de-mapper block 1118 may receive symbols from a plurality ofcarrier frequencies. The OFDM de-mapper block 1118 may distinctlyidentify each of the plurality of carrier frequencies. The OFDMde-mapper block 1118 may be operable to process symbols from each of theindividual carrier frequencies in a manner, which is substantiallysimilar to that described for the SCM de-mapper block 1116. In variousembodiments of the invention, the order in which the OFDM de-mapperblock 1118 may process symbols from each of the plurality of carriersmay be determined in response to frequency interleaving, which may havebeen performed at the transmitter 1000.

The de-interleaver block 1120 may comprise suitable logic, circuitryand/or code that are operable to rearrange the order of bits receivedfrom the OFDM de-mapper block 1118. The order of the rearrangement ofbits may be determined in response to bit interleaving, which may havebeen performed at the transmitter 1000.

The MUX 1122 may comprise suitable logic, circuitry and/or code that mayenable the MUX 1122 to receive input from the SCM de-mapper block 1116and the de-interleaver block 1120. The MUX 1122 may enable the dual modereceiver 1100 to receive signals utilizing an SCM PHY by selectivelyoutputting a signal, which is input from the SCM de-mapper block 1116.The MUX 1122 may enable the dual mode receiver 1100 to receive signalsutilizing an OFDM PHY by selectively outputting a signal, which is inputfrom the de-interleaver block 1120.

The inner de-coding and descrambling block 1124 may comprise suitablelogic, circuitry and/or code that are operable to decode and descramblereceived bits and generate decoded bits. The inner de-coding anddescrambling block 1124 may receive an inner coding type identifier asinput, which may be utilized to select an inner FEC type. The selectedinner FEC type may be utilized during processing of the received bits.

In operation, the prefix removal block 1106 may receive chips asdescribed above and output a time domain signal. The FFT block 1108 mayreceive the time domain signal from the prefix removal block 1106 andoutput a frequency domain representation of the time domain signal. Theequalization block 1110 may receive the frequency domain signal from theFFT block 1108 and output an equalized signal by performing signalequalization as described above. The IFFT 1112 may receive the equalizedsignal from the equalization block 1110 and output a time domainrepresentation of the equalized signal. The re-sampler and filter block1114 may receive the time domain signal output from the IFFT 1112 blockand output a resampled signal. The resampled signal may also befiltered. The resampled signal may comprise a symbol for each sample ina time sequence. The SCM de-mapper 1116 may receive the resampled signalfrom the re-sampler and filter block 1114 and generate bits as describedabove.

The OFDM de-mapper 1118 may receive the equalized signal from theequalization block 1110 and output bits as described above. Thede-interleaver block 1120 may receive bits from the OFDM de-mapper 1118and generate rearranged bits as described above. The MUX 1122 may selectbits from the SCM de-mapper block 1116 or from the de-interleaver block1120. The selected bits may be output from the MUX 1122. The MUX 1122may make a selection based on a signal from, for example, the processor406. The inner de-coding and de-scrambling block 1124 may receive bitsfrom the MUX 1122 and generate decoded bits as described above.

FIG. 12 is an illustration of exemplary preambles for MIMO operation, inaccordance with an embodiment of the invention. FIG. 12 presents anexemplary illustration of long sequence generation from a transmitter404, which utilizes a plurality of transmitting antennas 432 toconcurrently transmit signals. Referring to FIG. 12, there is shown anexemplary PDU 1200, which is transmitted by a first antenna in a MIMOtransmitter, and an exemplary PDU 1250, which is transmitted by a secondantenna in a MIMO transmitter.

The PDU 1200 may comprise a short sequence field 1202, a guard intervala (Guard_a) 1204, a Golay code sequence a (Seq_a) 1206, a guard intervalb (Guard_b) 1208, a Golay code sequence b (Seq_b) 1210, a header field1212, a Guard_a 1214, a Seq_a 1216, a Guard_b 1218, a Seq_b 1220 and apayload field 1222. The PDU 1250 may comprise a short sequence field1252, a cyclically shifted[[,]] Guard_a, Guard_a″ 1254, a cyclicallyshifted Seq_a, Seq_a″ 1256, a cyclically shifted Guard_b, Guard_b″ 1258,a cyclically shifted Seq_b, Seq_b″ 1260, a header field 1262, acyclically shifted complement Guard_a″, Guard_−a″ 1264, a cyclicallyshifted complement Seq_a″, Seq_−a″ 1266, a cyclically shifted complementGuard_b″, Guard_−b″ 1268, a cyclically shifted complement Seq_b″,Seq_−b″ 1270 and a payload field 1272.

In various embodiments of the invention, the cyclically shifted Guard_a′1254 may represent a cyclically shifted version of Guard_a 1204, thecyclically shifted Seq_a′ 1256 may represent a cyclically shiftedversion of Seq_a 1206, the cyclically shifted Guard_b′ 1258 mayrepresent a cyclically shifted version of Guard_b 1208 and thecyclically shifted Seq_b′ 1260 may represent a cyclically shiftedversion of Seq_b 1210.

In various embodiments of the invention, the cyclically shiftedcomplement Guard_−a′ 1264 may represent a binary complement version ofGuard_a′ 1254, the cyclically shifted complement Seq_−a′ 1266 mayrepresent a binary complement version of Seq_a′ 1256, the cyclicallyshifted complement Guard_b′ 1268 may represent a binary complementversion of Guard_b′ 1258 and the cyclically shifted complement Seq_−b′1270 may represent a binary complement version of Seq_b′ 1260.

Various embodiments of the invention may comprise a method and systemfor low rate OFDM encoding. Encoding of the OFDM symbols may utilize asubset of carriers available in an OFDM channel bandwidth. In anexemplary embodiment of the invention, which utilizes a 512-point FFTand IFFT, 32 carriers may be utilized. BPSK values may be assigned toeach of the 32 carriers based on a Golay code sequence, which isselected from a plurality of Golay code sequences. The Golay codesequences among the plurality of Golay code sequences may be maximallyseparated. For example, in an exemplary embodiment of the invention, theplurality may comprise 256 Golay code sequences, each of which comprisesa 32-chip sequence. An exemplary embodiment of the invention may utilizea spreading factor of 4, thus each 32-chip sequence may correspond to8-bits. Consequently, each OFDM symbol may correspond to 8 encoded bits.The encoded bits may represent encoded bits, which were generated byutilizing a selected inner FEC type, for example a coding rate ½ LDPC orcoding rate ¾ LDPC.

FIG. 13 is a block diagram of an exemplary IFFT algorithm for low rateOFDM encoding, in accordance with an embodiment of the invention.Referring to FIG. 13, an OFDM symbol may be generated by a 512-pointIFFT block 1302, by utilizing a subset of the taps available in the IFFTblock 1302. Each of the taps may correspond to a frequency carrier,which is utilized for transmission of bits in an OFDM symbol. As shownin FIG. 13, in an exemplary embodiment of the invention, there may be aspacing of 11 taps between selected frequency carriers. In variousembodiments of the invention, an offset value, q, may be utilized toenable a plurality of piconets to concurrently generate OFDM symbolswhile reducing the likelihood that OFDM symbols transmitted within onepiconet will interference with transmission of OFDM symbols in a nearby,or overlapping, piconet. In an exemplary embodiment of the invention,potential values of the offset value, q, may be −4, 0 and 4. Forexample, a parent piconet 222 may utilize low-rate OFDM encoding ofsymbols by utilizing an offset value of −4, while a nearby piconet mayconcurrently practice low-rate OFDM encoding of symbols by utilizing anoffset value of 4.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for communicating data, the method comprising: selecting aradio frequency (RF) channel and a physical layer type by a receiver ina communication device; processing signals received via said selected RFchannel, based on said selected physical layer type; determining whethera beacon protocol data unit has been detected, based on said processedsignals; establishing an association with an existing network when saidbeacon protocol data unit has been detected; determining a signal energylevel for said received signals when, based on said processed signals, aprotocol data unit has not been detected; and transmitting anoriginating beacon protocol data unit by a transmitter in saidcommunication device based on said determined signal energy level whensaid protocol data unit has not been detected.
 2. The method accordingto claim 1, comprising establishing said association with said existingnetwork by communicating with a coordinating communication device thatis associated with said existing network.
 3. The method according toclaim 1, wherein said selected physical layer type comprises a singlecarrier modulation physical layer or an orthogonal frequency divisionmultiplexing physical layer.
 4. The method according to claim 1,comprising processing said signals based on a subsequent physical layertype.
 5. The method according to claim 4, wherein said subsequentphysical layer type comprises a single carrier modulation physical layerwhen said selected physical layer comprises an orthogonal frequencydivision multiplexing physical layer.
 6. The method according to claim4, wherein said processing of said signals utilizes stored informationthat is known about said subsequent physical layer type.
 7. The methodaccording to claim 4, comprising determining whether a protocol dataunit has been detected based on said signals that are processed based onsaid subsequent physical layer type.
 8. The method according to claim 7,comprising selecting a subsequent RF channel based on said determinedsignal energy level and/or selecting said subsequent RF channel whensaid protocol data unit has been detected based on said signals that areprocessed based on said subsequent physical layer type.
 9. The methodaccording to claim 1, comprising starting a time duration at the startof said processing of said signals.
 10. The method according to claim 9,comprising transmitting said originating beacon protocol data unit, viasaid selected RF channel or via a selected subsequent RF channel,subsequent to expiration of said time duration.
 11. A system forcommunicating data, the system comprising: one or more circuits that areoperable to select a radio frequency (RF) channel and a physical layertype; said one or more circuits are operable to process signals receivedvia said selected RF channel, based on said selected physical layertype; said one or more circuits are operable to determine whether abeacon protocol data unit has been detected, based on said processedsignals; said one or more circuits are operable to establish anassociation with an existing network when said beacon protocol data unithas been detected; said one or more circuits are operable to determine asignal energy level for said received signals when, based on saidprocessed signals, a protocol data unit has not been detected; and saidone or more circuits are operable to transmit an originating beaconprotocol data unit based on said determined signal energy level whensaid protocol data unit has not been detected.
 12. The system accordingto claim 11, wherein said one or more circuits are operable to establishsaid association with said existing network by communicating with acoordinating communication device that is associated with said existingnetwork.
 13. The system according to claim 11, wherein said selectedphysical layer type comprises a single carrier modulation physical layeror an orthogonal frequency division multiplexing physical layer.
 14. Thesystem according to claim 11, wherein said one or more circuits areoperable to process said signals based on a subsequent physical layertype.
 15. The system according to claim 14, wherein said subsequentphysical layer type comprises a single carrier modulation physical layerwhen said selected physical layer comprises an orthogonal frequencydivision multiplexing physical layer.
 16. The system according to claim14, wherein said processing of said signals utilizes stored informationthat is known about said subsequent physical layer type.
 17. The systemaccording to claim 14, wherein said one or more circuits are operable todetermine whether a protocol data unit has been detected based on saidsignals that are processed based on said subsequent physical layer type.18. The system according to claim 17, wherein said one or more circuitsare operable to select a subsequent RF channel based on said determinedsignal energy level and/or select said subsequent RF channel when saidprotocol data unit has been detected based on said signals that areprocessed based on said subsequent physical layer type.
 19. The systemaccording to claim 11, wherein said one or more circuits are operable tostart a time duration at the start of said processing of said signals.20. The system according to claim 19, wherein said one or more circuitsare operable to transmit said originating beacon protocol data unit, viasaid selected RF channel or via a selected subsequent RF channel,subsequent to expiration of said time duration.